Stabilization of photographic emulsions sensitized with gold compounds



Patented May 27, 1952 SIONS SENSITIZED WITH GOLD POUNDS COM- Rudolph E. Damschroder, Rochester, N. 11, as-

signor to Eastman Kodak Company, Rochester, N. Y., a corporation of New Jersey No Drawing. Application September 24, 1949, Serial No. 117,719

This invention relates to stabilization of photographic emulsions which are sensitized with gold compounds.

It is known that photographic silver halide emulsions can be sensitized by digesting the emulsions in the presence of gold compounds. The gains in speed thus obtained are clearly of value, but it has been found that coatings of such emulsions on the usual supports tend to lose speed on keeping or storage. I

I have. now found that the speed stability of coatings of emulsions sensitized with gold compounds can be markedly improved by the addition of at least one water-soluble gold compound to the g-old-compound-sensitized emulsions after,

the final digestion of the emulsions but before coating the emulsions on a support. The addition of the water-soluble gold compounds after final digestion, but before coating doesnot increase the initial speed of the emulsion, but rather stabilizes the already sensitized emulsions against speed loss on keeping or storage of the coated emulsions.

It is, accordingly, an object of my invention to provide photographic emulsions sensitized with gold compounds, which emulsions have improved resistance to loss of speed, i. e. sensitivity, on keeping or storage. A further object is to provide a process for preparing such improved emulsions. Other objects will become apparent hereinafter.

The usual procedure for preparing photographic silver halide developing-out emulsions, especially photographic gelatino-silver-halide developing-out emulsions, comprises the following stepsz (l) Precipitation-Wheiein the silver halide is precipitated by the interaction of a watersoluble silver salt and 'a water-soluble halide, in the presence of a carrier, e. g. gelatin.

(2) Digestin.Wherein the above precipitate is heated for a period of time at a raised temperature, e. g. 50 to 60 C., with or Without the addition of further carrier, e. g. gelatin.

(3) W ashing.Wherein the digested, solidified or set (e. g. by chilling) emulsion is washed to remove soluble salts.

(4) Melting out and second digestion.Wherein the washed emulsion is melted and the resulting fiowable emulsion is heated for aperiod of time, with or without the addition of further carrier, e. g. gelatin.

Of course, variations of the above four steps can be employed. An emulsion, when used without Claims. (CI. 957) I employing a step, such as (3), I call an unwashed,

" of emulsion generally used.

During the last step, i. e. the melting-out and second or final digestion, the emulsion increases in sensitivity. To increase the speed of photographic emulsions various substances have been added at various stages in the preparation of the emulsions. Usually the additions are made during one of the digestion periods Frequently sulfur compounds, i. e. so-callecl sulfur sensitizers have been added, e. g. allyl isothiocyanate, sthioure'a, thio'carbanilide, etc., have been added.

More recently, it has been proposed to employ ammonium and/or metal thiocyanates for this purpose. Still more recently gold compounds have been proposed for the same purpose. It is with these photographic silver halide emulsions which during their preparation have been sensitized by digestion in the presence of gold compounds with or without the additional presence of a sulfur s'ensitizer, that my invention is concerned.

In accordance with my invention, I incorporate in a photographic silver halide emulsion (which during its preparation has been sensitized by digestion in the presence of a gold compound) at least one water=soluble gold compound which has a solubility in water greater than the equivalent of 1.0 mg. of gold (metallic) per ml. of water at 25 (2., after the final digestion of the emulsion and before coating the emulsion on a support.

Typical of the water-soluble gold compounds are:

I. Potassium chloroaurate, KAuCll II. Auric trichloride, AuCls III. Myochrysine (gold sodium-thiomalate) IV. Potassium aurithiocyanate, KAu'(CNS)4 V. Solganal-B oleosum (aurothioglucose in sesame oil) VI. Pyridino-trichlorogold, (CtHsN)AuCla-HC1 VII. Trichlorogold-dimethyl sulfide,

IX. Diethyl-monobrom-gold, Au(C2H5)2Br X. Monochlorogold-dimethyl sulfide,

AuCl- (CH3) 2s XI. Potassium aurothiocyanate, KAu(CNS)2 The water soluble gold compounds can be added to the emulsions in the form of solutions in suitable solvents, e. g. water, methyl alcohol, ethyl alcohol, acetone, etc., or as dispersions in colloids, such as gelatin, polyvinyl alcohol, partially hydrolyzed cellulose acetate, casein, etc., or without any solvent or colloid. The water soluble gold compounds should, of course, be thoroughly dispersed throughout the emulsions, e. g. by stirring.

Ordinarily, it is advantageous to employ a concentration of the water-soluble gold compound equivalent to from 1.5 to 20 mg. of metallic gold per 1000 g. of silver nitrate used in preparing the emulsion. However, lower or greater concentrations can be employed, e. g. a concentration equivalent to 1000 mg. of metallic gold per 1000 g. of silver nitrate used in preparing the emulsion.

The water-soluble gold compounds are advantageously added to the emulsions after the final digestion, but prior to coating the emulsions on a support, at a pH of from 5 to 9, and most advantageously at pH of from 6 to 7.

The following examples will serve to illustrate further the manner of practicing my invention.

EXAMPLEl A batch of gelatino-silver-bromoiodide emulsion was prepared as described by Trivelli and SmithPhot. J. 79, 330 (1939), using a precipitation time of about minutes (emulsion No. 11,

page 330), except that just before the final digestion of the emulsion, potassium chloroaurate (KAuCh) in a concentration equivalent to 6.5 mg. of metallic gold per 1000 g. of silver nitrate employed in preparing the emulsion, thiosinamine in a concentration of 50 mg. per 1000 g. of silver nitrate employed in preparing the emulsion, and sodium thiocyanate in a concentration of 1 g. per 1000 g. of silver nitrate employed in preparing the emulsion, were added to the emulsion. A portion of the emulsion was coated on a cellulose acetate film and dried. The film was cut into two portions. One portion was kept no longer than for the short time (few hours) at about 70 F. required for the routine of exposing the film in a II) sensitometer at 2 second exposure, using 100 watt, sunlight quality illumination and developing the exposed film. in Eastman Kodak Companys D-19 developer for 4 minutes at 20 C. The results of this exposure and development are given in Table A below. The other portion was subjected to an accelerated keeping or incubation treatment wherein the coated film was stored or kept for 7 days at 120 F. At the end of this period, the incubated film was exposed and developed as described above. Results are recorded in Table A below. 7

To further portions of the same emulsion after final digestion and before coating the portions of emulsion on cellulose acetate films various watersoluble gold compounds were added as shown in Table A below. The coated films were cut into two portions and one portion exposed and developed in the routine manner described above. The other portion was subjected to an accelerated keeping or incubation treatment wherein the coated film was stored or kept for 7 days at 120 F. At the end of this period, the incubated film was exposed and developed as described above. Results are recorded in Table A below.

Table A later-solullekglold ompoun ter Keeping Speed Final Digestion Gamma F0 of g 01 (1 per Treatment (1/1) g 1000 g. of AgNO:)

1 none {routine 0. 0. 7 days at 120 F 33 0.73 0. 2 I 2 5 routine 71 0. 91 0. 7 days at 120 F 37 0.82 0. 3 I 7 5 routine 69 1. 04 0. 7 days at 120 F 80 0.80 0. 4 I 20 routine 73 1.05 0. I 7 days at 120 F... 108 0.87 0. 5. I, 50 2g 8 g" 82 0.87 0. IL {7 ci at 120 35 0.83 0. ton ine 69 0. 98 0. {7 days at 120 49 0. 91 0. rou ine 71 1.02 0. 20 {7 datys at 120 82 0. 88 o. rou me 78 0.93 0. 5 {7 da s at 120 so 0. 94 0. rou ine 69 0.96 0. {7 days at 120 F as 0. 79 0. rou me 78 1.02 0. {7 days at 120 94 0. 92 0. rou me 73 0. 96 0. {7 days at 120 39 1.12 0. rou ine 73 0. 0. M 7 days at F 44 1.00 0. rou me 52 1.14 0. 20 7 days at 120 7s 0. 91 0.

From the data in the foregoing table, it is apparent that the emulsion which was sensitized by digesting in the presence of the gold compound, thiosinamine and sodium thiocyanate had a high initial'speed of 80 as shown at 1. After subjecting this emulsion to an accelerated keeping treatment, however, the emulsion had lost a very large fraction of its speed (sensitivity) as shown at 1. On the other hand when potassium chloroaurate (I) was added to the same emulsion, in a concentration equivalent to 2.5 mg. of gold,

46 after final digestion but before coating, the initial speed (71) of the emulsion was reduced to only 37 after the same accelerated keeping treatment, as shown at 2. When potassium chloroaurate (I) was added to the same emulsion, in a concentration equivalent to 7.5 mg. of gold, after final digestion but before coating, the initial speed of 69 was not reduced at all after the same accelerated keeping treatment as shown at 3. Actually, in this last instance, there was a gain rather than a loss in speed after the accelerated keeping treatment. It is to be understood, of course, that the accelerated keeping treatment is drastic and that such severe conditions would rarely be encountered in practical keeping or storage of products comprising sensitized emulsions. The other data given in the above table at 4 to 14 show further beneficial retardation of loss of speed that can be attained in accordance with my invention.

EXAMPLE 2 A batch of gelatino-silverbromoiodide emulsion was prepared as described by Trivelli and Smith--Phot.. J. 79, 330 (1939), using a precipitation time of about 20 minutes (emulsion No. 11, page 330), except that just before the final digestion of the emulsion potassium chloroaurate, thiosinamine and sodium thiocyanate were added to the emulsion in the concentrations shown in Example 1. A portion of the emulsion was coated on cellulose acetate film and dried. The film was cut into two portions and the one portion exposed and developed in the routine manner shown in Example 1 while the other portion was incubated and then exposed and $502806" 5 a. H dhvelopedi 'asflshbwn in. 1.: --Results; are about? 20 C; and. then: chilled. to 096C; Thezsolid recordedtirn TablzB bel'ow. was collected on a filter and washed with acetone;

To further portionsfthe same; emulsions-after fiiralx-digestion and' beforef coating;-

portions of emulsion om" cellulose a acetate various: water-soluble gold: compounds? were added'as shown. in. Tabler B below. The coated films were cut into" two portion's andi one portion. -.exposed. and developed im the: routinemarinerdescribed Example I. other portions; were-incubated/and thenexposed and; developed. as describedin: Example L. Riesultsi are: recorded in Table'B'below.

Tabla B viewer-8011131 gold.

bmpmm Keep'lii Speed Final Digestion. 1 *sGsm'ma gFog: (in; Qfigotdper" Conditions 1000=g-; ofiRgNOz) routine 76 j 0390 5 006 {7 days at 120 35 0. 92 0. 16 v routineu u, i 79 0. 91 0.05 I 7 days, at 120? F, 58 0. 97 0. 17 V 30 {routinem 76 0.89 0.05 I 7 days at 120 F 59 0. 92 0. 19 V 100 {routineh' 68 1.00 0.07 7 days at 120F 90 1. 02 0- 25 VI 5 74 0.92 0.07 V a p 63 0. 99 0.16 VI routine 74 1.00 0.07 v 7 days at 120 F--- 59 68 1. V1, 30 0.85 8. 31 utln 66 0.95 6 0 tc c9e= X 7r 1 1.0a VII,-15L Q m 24 '68 1.04" can V1150 73.. i 0.92. 0;.33 019 0.10' -r g (ne 0125 7 65 1:02. 0.10

. G]; I l 5 4' I 50 47. 1 0,78. 01.38 56- LOl. 0.04 45 0175: 18 4-5 0:99 0102 V 46 0' '15 0 1'0 As in Table A, the'above1-data Table. 3 show further the beneficial retardation of loss of speed that can be attained in accordance with my invention.

Any gold compound having a solubility in water greaterthari the equivalent of 10mg. of gold per 100ml. of-water at 25 C. and be employed to add to the gold-compound-sensitized emulsions after final digestion but priorto coating of the emulsion, in accordance with my invention. Many of such water-soluble gold compounds are described in the chemical'literature. For-example. monoc'hlorogold diinethylsulfidti' is described by Ray and Sen-J. Indian Chem. Soc. 71] "72 "(1930) Diethy1=m0nobrom'-'-g0Id" is described by Pope and Gibson- 0. Chem." Soc. 91,, 2061"-2'06 3 (1907). Trich-lorogo'ld dimethylsulfide is described by Ray and Sen-0. IndianChem. see. 7, '72-'61930); Pyridino-tri'chlorogold is described by Gmelin-Kraut llandbuch der' Anorg. Chem; V2; p. 292-3411;. Pyridinotrichloro gold andstill other of the water-soluble gold"compounds" can be" prepared as" shown the fol lowing examples.

A solution containing 1 g. of gold chloride in 95% ethyl alcohol. was added to a solution containing 0.79 g: or pyridine in "1.0 octet/95% ethyl alcohol. A cream solid separated at once. The reaction mixture was stood forrseveral hours at The yield of cream crystals was 79% crude and 20% after two recrystallizations from acetone.

EXAMPLE 4 I A solution containing 1 g. of gold chloride (AuCls) in 10 cc. of: absolute ethyl alcohol was added to a suspension of 0.93 g. of 3,3'-dimethylthia carbocyanine" chloride in 2000. of absolute ethyl alcohol. .A brown. solid separated at once. After chilling for 30 minutesat 0 C., the solid was collected on a filter and washed with absolute ethyl alcohol. The yield of the gold compound formulated above was83'% crude and 59% after one recrystallization from 'nitromethane. The dark blue needles-gave av bluish-red solution-in acetone.

In a. manner similar to that illustrated in the foregoing Example 4 other water solublevgold compounds can be prepared from cyaninev dyes- However, a great many of the gold. compounds thus prepared from eyanine dyes.- are waterinsoluble, i-. e. they have a solubility inwater less. than theequivalent of 1.0 mg. of gold per 100. ml. of water at C.

Alkali metal chloroaurates', e. g. potassium and sodium chloroaurates, are well known substances. as. is auric trichloride and alkali metal aurithiocyanatesand alkaliv metal aurothiocyanates. Myochrysine is a. product of Merck &. Company and Solganal-B oleosum is a product. of Scheri'ng Corporation.

My invention can be practiced onphotographi'c silver halide emulsions which have been. sensi tizedby digesting the emulsions in. the presence of either water-soluble or' water-insoluble; goldcompounds. Asshown above the sens'i'tizatiori of emulsions by digesting with water-soluble. gem compounds is well known. Toso sensitize amen sions, at leastone water soluble goidcompofund, e. g. any or: the water-soluble gold compounds set forth above, is added tothe emulsion prior'to or during the final digestion. Advantageously'the concentration of the gold compound is equivz'a-len't to from 2.5 to 1000 mg. of gold per 1000 g. of silver nitrate used in preparing the emulsion. Most advantageously a concentration of water-soluble gold compound equivalent to from 2 tomg. of gold per kilogram of silvernitrate used in' preparing the emulsion is employed.

Advantageously the level of pH during thedigestion of the emulsion, in the presence of the water soluble gold compound, is maintained 'ator below 9. although this is not essential. Generally speaking, the best results are obtained by digesting the emulsions at a pH of from 5 to 9, the presence of the water-soluble gold compound. Digestion-of the emulsions in thepresence of the gold compounds is advantageously efiected at from-'C. tot-5 0., although other temperatures can be used. A temperature range of to C.

ordinarily gives the best results.

Advantageously the emulsions sensitized by di-- gesting with the water-soluble gold compounds are digested the additional presence of at least one sulfur compound e. g. a sulfur sensitizer; for

instance an organic compound containing a C=S ora group. Typical of such sulfur sensitizers are:

S I CHz=CHCHzNH( JNH Thiosinamine (Allythiourea) S -CH2CH(NH2) C O OH Cystine Normal gelatins contain small amounts of sulfur compounds, such as thiosinamine or allylisothiocyanate, but it is nevertheless frequently advantageous to add to the gelatin emulsions additional sulfur sensitizers.

Beneficial efiects are also obtained by digesting the emulsions which are sensitized by digestion in the presence of a water-soluble gold compound, in the additional presence of at least one metal or ammonium thiocyanate, e. g. alkali metal thiocyanates (e. g. sodium or potassium thiocyanate), alkaline earth metal thiocyanates (e. g. calcium, strontium thiocyanate, etc.) cadmium thiocyanate, ammonium thiocyanate, etc. Of course, thiocyanates containing cations which cations are known to have, in themselves, a deleterious effect on silver halide emulsions should be avoided. Otherwise, the beneficial effects attained with the thiocyanates would be partially nullified by the deleterious action of the cation. Thus iron thiocyanate which contains the iron cation should be avoided. One or more sulfur sensitizers or one or more thiocyanates selected from the group consisting of metal or ammonium thiocyanates can be employed. One or more sulfur sensitizers can be employed in conjunction with one or more thiocyanates containing a cation selected from the group consisting of metal and ammonium cations. The sulfur sensitizers and thiocyanates are advantageously incorporated in the emulsions in the form of their solutions in a suitable solvent, such as water, methyl or ethyl alcohol.

The sulfur sensitizers can be incorporated in the emulsions at any stage of the preparation of the emulsions, e. g. during precipitation of the silver halides, during the first digestions (ripening) or during the second digestion of the emulsions. When incorporating metal and ammonium thiocyanates in the emulsions prior to washing, the amount can vary Widely. Advantageously, however, an amount of thiocyanate equal to from about to about 75 g. per kilogram of silver nitrate used in preparing the emulsion is employed. If the thiocyanate or sulfur sensitizer is not added until later in the preparation, e. g. after washing, it is advantageous to employ, in the case of the thiocyanates, an amount equal to from about 0.1 to about 10 g. per kilogram of silver nitrate used in preparing the emulsion and in the case of the other sulfur sensitizers, an amount equal to from about 0.01 to about 10 g. per kilogram of the silver nitrate used in preparing the emulsion It is advantageous to digest, i. e. to heat treat, the emulsion withboth the water-insoluble gold compound and the sulfur sensitizer or thiocyanate present, at an appropriate temperature, e. g. at from 100 to 150 F. During digestion, i. e. the seconddigestion as contrasted with the first digestion or ripening, the pH of the emulsion is advantageously adjusted to between 5 and 7.

Typicalwater-insoluble gold compounds with which photographic silver halide emulsions can be sensitized by digesting the emulsions in the presence thereof are described in the following examples. To sensitize emulsions with these water-insoluble gold compounds, the procedures (e. g. pH, temperature, sulfur sensitizers, thiocyanates, etc.) set forth above for sensitizing emulsions with water-soluble gold compounds can be employed.

EXAMPLE 5 A solution containing 0.33 g. of auric chloride in 10 cc. of ethyl alcohol was added to cc. of 95% ethyl alcohol containing 0.85 g. of 3-ethyl- 2-(3) -thiothiazolo[4,5-bl quinolinone (prepared by heating 3-ethy1rhodanine and o-aminobenzaldehyde in acetic acid solution according to Granacher et al.-Helv. Chim. Acta 8, 890 (1925)). The above-formulated compound precipitated and after the reaction mixture stood for several hours at 20 C'., the product was collected on a filter and washed with 95% ethyl alcohol. The yield of light cream crystals was 75% after one recrystallization from acetic acid.

EXAMPLE 6 c1 oo- 1 I-o,m =on-o H=t SAu A solution containing 0.34 g. of auric chloride in 10 cc. of 95% ethyl alcohol was added to a EXAMPLE '7 .A solution containing 0.5 g. of auric chloride in- 10 cc. of 95% ethyl alcohol was added to a hot suspension of 1.61 g. of'3-ethyl- -(3 ethyl- 12(3)-benzothiazolylidene) rhcdanine in '25 ccmot' acetic acid. The reaction mixture was .stood several hours at about 20 C. and the precipitated solid was filtered off and washed on the filter with 951% ethylalcohol. The washed solid was extracted with 180 cc. of hot nitromethane. Upon chilling the hot extract, the crystals which formed were filtered oil and recrystallized from 155 ce. of nitromethane. The yield of golden yellow crystals was almost 100%.

EXAMPLE 8 C 111 A 11C14 ,A solution containing 1 .g. of auric chloride in 110 cc. of absolute ethyl alcohol was added .to a solution "containing 0.66 g. of 2-;methyl-c-naph- :thothiazole ethochloride in '10 cc. of absolute ethyl-alcohol. A pale yellow solid separated at once; After chilling for one .hour at. 0 (3;, the solid was collected on .a filter and washed with absoluteethyl-alcohol. The yield of product was 92% crude and 53% after one recrystallization from nitromethane. The yellow needles gave a very pale yellow solution in acetone.

jHs

A solution containing '1 got :auric chloride in cc. of-absolute ethyl alcohol was added-toe.

' solution containing 0.90 g. of l,l' -diethyl-2,-2"-

cyanine chloride in cc. of absolute ethyl alcohol. A reddish solid separated at once. After chilling for one hour at 0 C., the solid was collected on a filter and washed with absolute ethyl alcohol. The yield of dye was 72% crude and 45% after one recrystallization from nitromethana-z The dark green crystals gave a pink solu'- tion acetone.

After chilling for one L in EXAMPLE 11 EXAMPLE 1'2 O H5 AllCll A solution containing 1 g. of auric chloride .in cc. .of absolute ethyl alcohol was .added :to a suspension of 0.92. g. for :1Q3-diethylthiae2".=;cyanine chloridein .20 cc. of absolute ethyl alcohol. An orange solid separated at once. After chilling .for one hour at 0 C., the solid wascollected-on a ,filter and washed with absolute ethyl alcohol. The yield of dye was 89% crude and 571% after one recrystallization from mitrome'thane: The reddish coppery needles gave an amber solution in acetone.

A solution containing 1 g. of auric chloride in 10 cc. of absolute ethyl alcohol was added to a suspension of 0.93 g. of 3g3--diethylth-iacyanine chloride in 20 -cc. of absolute ethyl alcohol. A pale orange solid separated at once. After chilling for one hour at 0 0., the solid was collected on a filter and washed with absolute ethyl alcohol. The yie'ld of dye was 56% crude and 38% afteone recrystallization from nitromethane. The deep red crystals with a blue reflex gave a pale yellow solution in acetone.

In a manner similar to that shown in Examples 4 to 13-, other similar organic water-insoluble gold compounds can be prepared. In the heterocyclic nuclei of the organic gold compounds set forth in Examples 4 to 13, one or more of the hydrogen atoms can be replaced by a chlorine, a bromine or an iodine atom or by an .alkyl or and group, e. g. methyl, ethyl, phenyl, etc. Still A dark solid was formed at once.

11 II, part I, page 822 and by Gmelin-Kraut-W, page 271 (A); and 14111 which is described by Mellor, loc. cit. page 608 and by Gmelin-Kraut V2, page 282. I

Sensitizing dyes of all types can be employed to spectrally (optically) sensitize my new stabilized emulsions, e. g. erythrosin, Congo Red, any of the sensitizing cyanine dyes (monomethine, trimethine, pentamethine, heptamethine, etc.), and any of the sensitizing merocyanine dyes (see United States Patent 2,078,233, dated April 27, 1937 for example), any of the sensitizing hemicyanine dyes (see United States Patent 2,166,736, dated July 18, 1939, for example), any of the sensitizing hemioxonol dyes (see United States Patent 2,216,441, dated October 1, 1940 and United States Patent 2,165,339, dated July 11, 1939, for example), etc.

My new stabilized emulsions can be coated in the usual manner on any suitable support, such as glass, cellulose nitrate film, cellulose acetate film, polyvinyl acetal resin film, etc. to desired thickness, and then set in the usual manner. Hardening agents, setting agents and supersensitizing combinations of sensitizing dyes or a supersensitizing combination of one or more sensitizing dyes and another substance can be added to the emulsions.

Emulsions in which the carrier for the silver halide is other than gelatin and which have been sensitized by digesting in the presence of a gold compound can be stabilized in accordance with my invention. Among such non-gelatin silver halide emulsions are silver halide emulsions prepared using as the vehicle or carrier polyvinyl .alcohol (polyvinyl alcohol is herein intended to include all water-soluble hydrolyzed polyvinyl esters containing an ester group content equivalent to from to by weight of polyvinyl ester) silver halide emulsions prepared using as the vehicle or carrier hydrolyzed polyvinyl acetate containing an acetate group content equivalent to from 59 to 71% by Weight of polyvinyl acetate; silver halide emulsions prepared using as the vehicle or carrier polyvinyl acetals containing a large proportion of polyvinyl alcohol hydroxyl groups, e. g. polyvinyl acetaldehyde acetals containing polyvinyl acetaldehyde acetal group equivalent to at least 50% by weight of polyvinyl acetaldehyde acetal and polyvinyl alcohol hydroxyl groups equivalent to at least by Weight of polyvinyl alcohol, polyvinyl propionaldehyde acetals containin polyvinyl alcohol h droxyl groups equivalent to from to by weight of polyvinyl alcohol, and polyvinyl bucarrier in preparing my non-gelatin silver halide.

emulsions. Moreover, any other resinous or 001- loidal material soluble in any ethylalcohol-water mixture or in water, as stated above, can be employed in preparing my non-gelatin silver halide emulsions, e, g. soluble polyamide resins, such as described in United States Patent 2,384,072, dated September 4, 1945, and hydrolyzed copolymers of vinyl estersand ethylene-or 12 propylene, such as described'in United States Patent 2,397,866, dated April 2, 1946. Still further examples of colloidal materials which can be employed as vehicles or, carriers in preparing my non-gelatin emulsions are hydrolyzed cellulose carboxylic esters, such as hydrolyzed cellulose acetate or hydrolyzed cellulose acetate propionate, containing from 19 to 33% by weight of acyl groups, for example. Any cellulose compound, especially those containing only carbon, hydrogen and oxygen atoms, or those containing only carbon, hydrogen, oxygen and amino nitrogen atoms or ammonium nitrogen atoms, which is soluble in a mixture of ethyl alcohol and water (containing from 0 to 50% by volume of ethyl alcohol) to the extent of 10 g. per g. of solvent can be employed as the vehicle or carrier in preparing my non-gelatin silver halide emulsions.

In connection with the non-gelatin colloidal materials, such as polyvinyl alcohol, the silver halide emulsions can be prepared using gelling agents, such as phenols, e. g. orcinol, gallic acid, 2,4-dihydroxybenzoic acid, 4-chlororesorcinol, a-naphthol, phloroglucinol, 2,7-dihydroxynaphthalene, etc. Moreover, the non-gelatin silver halide emulsions can be prepared using silver halide dispersing agents, e. g. starch acetate, gum arabic, a copolymer of maleic anhydride and vinyl acetate, low viscosity methyl cellulose, water-soluble amino carbohydrate dispersing agents (e. g. diethanolamine cellulose acetate or any, other of these agents described in United States Patent 2,360,238, dated October 10, 1944) amino resin dispersin agents (e. g. dimethylaminobenzaldehyde acetals of polyvinyl alcohol, or Water-soluble polyvinyl acetals in which at least a part of the acetal groups are 4-formylphenyltrialkylammonium salt acetal groups, such as the polyvinyl acetal of 4-formylphenyl trimethylammonium methylsulfate and other such compounds described in United States Patent 2,358,836, dated September 26, 1944), etc.

Polyvinyl compound silver halide emulsions and their preparation are described in United States Patents 2,286,216, dated June 16, 1942; 2,276,322. dated March 17, 1942; 2,276,323, dated March 17, 1942; 2,311,058, dated February 16, 1943; 2,311,059, dated February 16, 1943;

2,367,511, dated January 16, 1945; 2,376,371, dated May 22, 1945 and 2,110,491, dated March 8, 1938.

Non-gelatin proteins can also be employed as vehicles or carriers in preparing the silver halide emulsions which are stabilized in accordance with my invention. Proteins, such as casein, soybean protein, blood albumin, egg albumin, castor bean protein, globulin and edestin are examples of such non-gelatin proteins, Non gelatin proteins which have been converted to a derivative thereof, e. g. by reaction with a sulfonyl chloride, a carboxylic chloride, a carboxylic anhydride, an isocyanate, a 1,4-diketone or acrylonitrile, and then oxidized, e. g. with hydrogen peroxide, can also be employed.

Myinvention is directed. especially to the stabilization of photographic silver halide emulsions which have been sensitized by digestion in the presence of at least one gold compound (watersoluble or water-insoluble) and in which the silver halide is principally silver bromide, but can be employed with any silver halide emulsion which has been so sensitized, particularly with the customary silver chloride, silver chlorobromide, silver chlorobromoiodide, silver chloroiodid'e, silver bromide and silver bromoiodide .de-.-'

tized. By the '.termfphotographic .silver. halide emulsion in which thesilver .halide is principally silver .r-bromide, meaniza :photographic .silver halide. emulsion in which from 60 to 100% of the of thesilver halidefis .silver bromide;

Eastman Kodak .Companys "D.-19 developer haszthe followin composition:

Water. -1 liters 2.0 .Ni-me'thyl p-aminophenol sulfatmgrams 8.8 Sodium .sulfite. desiccated--. 1do 38.420 Hydroquinone j do 35:2 fsodiumcarbonate, ,desiccated d 192.0 Potassium bromide; do .20i0 Water tojmake liters 4.;0

Whatihclaimzas mysinvention anddesire'to be secuned ibYELEttGI'S Patentofthe United States is:

j 1-..iA..;pr.ocess .:for stabilizing against :loss' zrof speed. =18; .photographic. silver halide. emulsion :hasl-been sensitized aby digesting the..=emulsionrin athe :presence .of .-.a :gold .comp'ound, .comprising adding :to :the gold-rcompound-sensitized ..-emnlsim1.5after :th'e ifinal. :digestion of the .emul- .sionibut prior :to .coastmg itheemulsion on :a sup- 1 port, era mater-soluble gold compound which ."has a solubility waiter greater than the equivalent of 1.0 mg. of gold per 100 ml. of water :at.25 C.

2. A process for stabilizing against loss of speed a photographic gelatino-silver-halide developing-out emulsion which has been sensitized by digesting the emulsion in the presence of a gold compound, comprising adding to the goldcompound-sensitized emulsion after the final digestion of the emulsion, but prior to coating the emulsionona supper-ta water-soluble gold compound which has a solubility in water greater than the equivalent of v 1.0 mg. of gold per 100 ml. of water 'at' 25 C.

3. A process for stabilizing against loss of :speed --a photographic gelatinmsilver-halide developing-out emulsion which has been sensitized flby...di'gesting the emulsion in the presence of a gold compound, comprising adding to the-goldcompound-sensitized cemulsion, :at .a :pH of irom I 5 to 9, after the final digestion of the emulsion, .zbut prior to coating the emulsion ion a support, a water-soluble gold compound which has asolubility Lin-water greater than the equivalent of 1.0 mg. of gold per 100 ml. of water at 25 C.

tized by digesting the emulsion in the presence of a ,goldcompound, comprising addin to the ,goldcompound-sensitized emulsion at a pH of from 5 to 9, after :the final :digestion of the emulsion, but prior to coating the emulsion on a support, a water-soluble gold compound which has a .solub'i'lity in water greater than the equivalent of 1.0 mg. of gold per 100 ml. of water at 25 C., the concentration of the water-soluble gold compound being equivalent to from 1.5 to 20 mg. of gold per 1000 g. of silver nitrate used in preparing the emulsion.

5. A process for stabilizing against loss of speed a photographic gelatino-silver-bromoiodide developing-out emulsion in which the silver halide is principally silver bromide, which has been sensitized by digesting the emulsion in the presence of a gold com-pound, comprising adding to the gold-compound-sensitized emulsion at a pl-I of from 5 to 9, after the final digestion of the emulsion, but prior to coating the emulsion on "a welop'ing-ioutemulsions which :haveibeen .so sensi- 1114 support, :a' rwasteresoluble :gold compound. which "has .a solubility .in waterrgreater than the equivalerit .of 1.10 11'lg.a0f gold per .160 ml. of waterqat 25 10., the concentration'iof the 'watterasolnble gold compoim'd ibeing equivalent to .fromtlfi ato 202mg. of gold per 1000 g of :silvernitrate used in preparing the emulsion.

56.411 rprocess' 'for'stabilizing .against. floss. of speed a photographic gelatino-silver-halide .de- 'velopingeout emulsion :in' which :the silver. halide 'is principally silver shromid'e, "which has been :sensitized lbw-digesting. the emulsion in the presence of 1a gold-compound :and -.a sulfur. :sens'itizer, nomprising adding to the tgoldecompoundesensitized .ennrlsion salt a pH v.oi from 5 to 9, :after thelfinal digestionof the emulsion, but prior to coating the .-.emulsion on :a :support, a water-soluble sgold compound which has :a solubility in water greater than the equivalent of 1.0 mg. of gold per 1003:1111. of-meter :at 25 (1., the .concentration aof fiche wateresoluble gold compound being equivalent "to from 1.5 to 20 mg. of gold per 1000 g. of silver nitrate .used in preparin the emulsion.

"'7. processfor stabilizing against lossof speed .a photographic :gelatino-silver=bromoiodid developing-out :emulsion in which the silver halide iszprincipally silver :brom'ide, which has been sensitizedby digesting the emulsion .in the presence :of a goldv compound :and a sulfzursensitizer, com- "prising adding .to the gold-compound-sensitized :emulsionat a pI-Iiof from toi9, a iterthefinal digestion of the emulsion, :but prior to coating :the

:emu-lsionon a support, a water-soluble gold compallysilver bromide, which has been sensitized by digesting the emulsion in the presence of ;a gold compound and a thiocyanate selected from the group consisting of alkali metal and ammonium thiocyanates, comprising adding to the goldcomp'ound-sensitized emulsion at a pH of from 5 'to 9, after the final digestion of the emulsion, but prior to coating the emulsion on a support, a water-soluble gold compound which has a-solubility *inwater greater than the equivalent of 1.0 mg.-of gold per 100ml. of water at 25 0., the concentration of the 'water soluble gold compound beingequivalen-t to from 1:5 to mg.--of gold per 1000 g.-- oi-silver nitrate used in preparing the emulsion.- 3

=9. Aprocessfor-stabilizing against loss-of speed a photographic gelatino-si1ver-brom0iodide 'developing-out emulsion in which the silver halide :is=pr'incipa11-y silver bromide, whichhas been sensitized by digesting the emulsion in the presence of a gold compound and a thiocyanate selected from the group consisting of alkali metal and ammonium thiocyanates, comprising adding to the gold-compound-sensitized emulsion at a pH of from 5 to 9, after the final digestion of the emulsion, but prior to coating the emulsion on a support, a water-soluble gold compound which has a solubility in water greater than the equivalent of 1.0 mg. of gold per 100ml. of water at C., the concentration of the Water-soluble gold compound being equivalent to from 1.5 to 20 mg. of gold per 1000 g. of silver nitrate used in preparing the emulsion.

10. A process for stabilizing against loss of speed a photographic gelatino-silver bromoiodide developing-out emulsion in which the silver halide is principally silver bromide, which has been sensitized by digesting the emulsion in the presence of a gold compound and a thiocyanate selected from the group consisting of alkali metal arid ammonium thiocyanates, comprising adding to the gold-compound-sensitized emulsion at a pH of from to 9, after the final digestion of the emulsion, but prior to coating the emulsion on a support, potassium chloroaurate in a concentration of from 1.5 to 20 mg. of gold per 1000 g. of silver nitrate used in preparing the emulsion.

11. A process for stabilizing against loss of speed a photographic gelatino-silver-bromoiodide developing-out emulsion in which the silver halide is principally silver bromide, which has been sensitized by digesting the emulsion in the presence of a gold compound and a thiocyanate selected from the group consisting of alkali metal and ammonium thiocyanates, comprising adding to the gold-compound-sensitized emulsion at a pH of from 5 to 9, after the final digestion of the emulsion, but prior to coating the emulsion on a support, potassium aurithiocyanate in a concentration of from 1.5 to 20 mg. of gold per 1000 g. of silver nitrate used in preparing the emulsion.

12. A process for stabilizing against loss of speed a photographic gelatino-silver-bromoiodide developing-out emulsion in which the silver halide is principally silver bromide, which has been sensitized by digesting the emulsion in the presence of a gold compound and a thiocyanate selected from the group consisting of alkali metal and ammonium thiocyanates, comprising adding to the gold-compound-sensitized emulsion at a pH of from 5 to 9, after the final digestion of the emulsion, but prior to coating the emulsion on a support, a water-soluble gold compound having the following formula:

potassium chloroaurate in a concentration of from 1.5 to 20 mg. of gold per 1000 g. of silver nitrate used in preparing the emulsion.

14. A process for stabilizing against loss'of speed a photographic gelatino-silver-bromoiodide developing-out emulsion in which the silver halide is principally silver bromide, which has been sensitized by digesting the emulsion in the presence of potassium chloroaurate, thiosinamine and sodium thiocyanate, comprising adding to the potassium-chloroaurate-sensitized emulsion at a pH of 5 to 9, after the final digestion of the emulsion, but prior to coating the emulsion on a support, potassium aurithiocyanate in a concentration of from 1.5 to 20 mg. of gold per 1000 g. of silver nitrate used in preparing the emulsion.

15. A process for stabilizing against loss of speed a photographic gelatino-silver bromoiodide developing-out emulsion in which the silver halide is principally silver bromide, which has been sensitized by digesting the emulsion in the presence of potassium chloroaurate, thiosinamine and sodium thiocyanate, comprising adding to the potassium-chloroaurate-sensitized emulsion at a pH of 5 to 9, after the final digestion of the emulsion, but prior to coating the emulsion on a support, a water-soluble gold compound having the following formula:

in a concentration of from 1.5 to 20 mg. of gold per 1000 g. of silver nitrate used in preparing the emulsion.

16. The emulsion obtained by the process of claim 1.

17. The emulsion obtained by the process of claim 3.

18. The emulsion obtained by the process of claim 4.

19. The emulsion obtained by the process of claim 6..

20. The emulsion obtained by the process of claim 12.

RUDOLPH E. DAMSCHRODER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,399,083 Waller et al Apr. 23, 1946 FOREIGN PATENTS Number Country Date 608,667 Great Britain Sept. 20, 1948 

1. A PROCESS FOR STABILIZING AGAINST LOSS OF SPEED A PHOTOGRAPHIC SILVER HALIDE EMULSION WHICH HAS BEEN SENSITIZED BY DIGESTING THE EMULSION IN THE PRESENCE OF A GOLD COMPOUND, COMPRISING ADDING TO THE GOLD-COMPOUND-SENSITIZED EMULSION AFTER THE FINAL DIGESTION OF THE EMULSION BUT PRIOR TO COATING THE EMULSION ON A SUPPORT, A WATER-SOLUBLE GOLD COMPOUND WHICH HAS A SOLUBILITY IN WATER GREATER THAN THE EQUIVALENT OF 10 MG. OF GOLD PER 100 ML. OF WATER AT 25*C. 